None of the current methods of assessing skeletal age include any data from U.S. white children after 1980, and these methods have never included data from U.S. black, Hispanic or Asian children. Skeletal age is an important clinical tool in the management of children with growth disorders, genetic syndromes and those receiving hormonal, orthopedic or orthodontic treatments. It is also a useful epidemiological variable that helps to account for maturational variance. By the early 1970's it was firmly established that the subjective Greulich-Pyle method did not accurately reflect the skeletal maturity of normal healthy U.S. children, and this was especially true for black children. The FELS Method for skeletal age of the hand-wrist of U.S. children was developed in the late 1980's based on the prevalence of ages for bone-specific maturity indicators from radiographs of white children in the Fels Longitudinal Study. However, these and all other available skeletal age methods are based on data that is at least 30 years old if not 60 to 80 years old such as the Greulich and Pyle method. There is a clear and pressing need for an accurate and valid method of assessing skeletal age applicable to the current, multi-ethnic population of U.S. children, and this can be achieved by updating the FELS method. Aim 1: To update the FELS Method for assessing the skeletal age of the hand-wrist. This will be accomplished by incorporating the age prevalence of grades of bone-specific indicators from 11,698 hand-wrist radiographs including 5,163 cross-sectional radiographs from 1,518 non-Hispanic white children, 1,376 non-Hispanic black children, 1,536 Hispanic children and 733 Asian-American children 0.08 to 22 years of age. Aim 2: To update the FELS skeletal age computer program, make race-specific adjustments, convert it to a current computer language and make a web-based version available. The FELS skeletal age method is the only method that uses a computer program to estimate skeletal age and provide standard errors. These new hand-wrist data will be used to adjust the algorithms in this program resulting in skeletal ages and standard errors appropriate for the multiethnic U.S. population of children and to provide race-specific skeletal ages as possible. Interactive access to this program on the world-wide-web will provide greater availability of this method to interested clinicians, epidemiologists and health care professionals. PUBLIC HEALTH RELEVANCE: None of the methods of assessing skeletal age available to clinicians and other investigators of growth and maturation of children include any data from U.S. children after 1980, and these methods have never included data from U.S. black, Hispanic or Asian children. All skeletal age methods are based on data that is at least 30 years old if not 60 to 80 years old such as the Greulich-Pyle atlas method. There is a clear and pressing need for an accurate and valid method of assessing skeletal age applicable to the current, multi-ethnic population of U.S. children. This need can be achieved by updating the FELS skeletal age method using recent available data from non-Hispanic white, non-Hispanic black, Hispanic and Asian American children.